The present invention relates generally to computer software, and more specifically, to a system and method of foiling buffer-overflow and alien-code attacks. The invention protects computers from such attacks by encoding data placed in storage, and varying the encodings used in different storage areas. When the data is needed by a software application, the data is simply decoded in a complementary manner. This prevents storage areas written according to one usage from being used effectively for some other purpose. The method of the invention can be done in a number of ways. For example, a "protector" engine can be placed between a software application and memory, or the function calls in the software application itself, could be amended to include encoding and decoding. Other embodiments and alternatives are also described.